Do rares in Pandaria phase out?

I've recently did a faction change and my faction quests reset. Atm I'm looking for Korda Torros for the gloves and chievement. He doesn't seem to spawn. may it be because i haven't done my new faction quest? there are the usual mobs in his location though

Are you sure he's just not dead/being killed? If you've been waiting longer than an hour and you haven't seen him at all there's probably something wrong. I'm pretty sure none of the rares are in phased areas.

Rare spawns aren't affected by phasing, the only rare spawn to be affected by phasing is ahone the wanderer right next to shado-pan monastary, and as said above, you need to complete the quest " beyond the wall".

I've done most zones on my 90 paladin and have then logged on my alts who haven't completed the zone and killed them, so I personally don't think they're phased, you're just unlucky.

I'm not sure if you know, but rares now spawn by zone, so if there aren't rares up in the zone you want, go round the other zones and kill every rare that's up in that zone until the rare you want is up, I use this trick all of the time, hence why I have 90% of the vanity items in Pandaria, the only ones I don't have are from valley of the four winds.

The western half of Vale of Eternal Blossoms is phased until you finish the breadcrumb quest that takes you to the Golden Pagoda to start your Golden Lotus dailies for the first time. The champions affected are Major Nanners, Ai-Ran the Shifting Breeze, Kang the Soul Thief, Urgolax, and Moldo One-Eye.

The eastern end of the Vale is not phased at any point, so Yorik Sharpeye and Sahn Tidehunter are never phased.

Likewise, the very westernmost end of the Vale right next to the Serpent's Spine and the Gate of the Setting Sun is actually not phased, so Kal'tik the Blight is never phased, either.

In Kun-Lai Summit, Ahone the Wanderer can be phased to you if you do some of the quests in Kun-Lai but don't do the followup breadcrumb quest into Townlong Steppes ( "Beyond the Wall" )

For some of these champions, it is possible to target them in an area where you are not phased to them, pull them, and then fight them in the area you aren't phased.

Korda Torros never has phasing issues, as far as I am aware. Make sure are looking in the right area for him - he spawns near Westwind Rest.